Relatively little is known about the molecular mechanisms involved in taste sensation; however, there are indications that both sweet and bitter taste detection involve G-protein mediated processes. Our goal is to understand the organization and control of taste signaling i.e. how individual pathways involved in taste transduction function and interact with each other. In the longer term we would like to define the components and the organization required for taste responses and to help elucidate the logic of taste coding. Specifically we would like to know what receptors mediate sweet and bitter taste; how tastant specificity and taste discrimination are accomplished; what topographic organization exists the various taste buds and papillae; and how the information is transmitted and encoded in the afferent nerves. Answering these fundamental questions would be aided by the isolation of genes involved in taste signaling, ideally taste receptors, that can be used to mark the cells, define the corresponding signaling pathways, dissect receptor specificity, generate topographic maps, and trace the respective neuronal connectivity circuits. We have identified and characterized two families of G-protein coupled receptors, T1Rs and T2Rs, that are expressed in distinct subsets of taste receptor cells and that are likely to be involved in bitter and perhaps sweet-taste responses. We are also interested in answering similar questions related to the sensation of volatile odorants (olfaction) and in these studies have focused on a large family of putative pheromone receptors (V2Rs) that we have identified.